1. Field of the Invention
The present invention relates to a substrate bonding apparatus for fabricating liquid crystal display (LCD) devices fabricated according to a liquid crystal dispensing method. More particularly, the present invention relates to a structure for securing substrates to stages (e.g., upper stages) of a substrate bonding apparatus.
2. Discussion of the Related Art
As the development of diverse types of information devices proliferate and become available to consumers, demands on the types of displays used by the information devices have increased. To meet such demands, many types of flat display devices including Liquid Crystal Display (LCD) devices, Plasma Display Panels (PDP), Electro Luminescent Display (ELD), Vacuum Fluorescent Display (VFD), etc., are currently being developed and, in some instances, actually employed as displays.
Among the various flat displays, LCD devices are commonly used as portable display devices. Due to their beneficial characteristics such as excellent picture quality (e.g., high resolution and luminance), light weight, thin profile, large display area, and low power consumption, LCD devices are commonly used in applications previously dominated by Cathode Ray Tubes (CRTs). Accordingly, LCD devices are commonly used in applications such as monitors of notebook computers, monitors of computers, and as TVs capable of receiving and displaying broadcasting signals.
Generally, LCD devices are fabricated using liquid crystal injection or liquid crystal dispensing methods. According to the liquid crystal injection method, opposing substrates are bonded together in a vacuum via a patterned sealant material formed on one of the substrates, wherein the patterned sealant material includes a liquid crystal injection hole. After being bonded, liquid crystal material is injected through the liquid crystal injection hole and between the bond substrates. Japanese Laid Open Patent Nos. 2000-284295 (Japanese Patent Application 1999-089612) and 2001-005405 (Japanese Patent Application 1999-172903) can be understood to teach a related art liquid crystal dispensing method wherein first and second substrates are provided and liquid crystal material is dispensed onto the first substrate. Subsequently, the first and second substrates are arranged to oppose each other, wherein the dispensed liquid crystal material is arranged between the opposing substrates. Lastly, the opposing substrates are bonded together in a vacuum.
FIG. 1 illustrates a related art substrate bonding apparatus for fabricating LCD devices using the liquid crystal dispensing method.
Referring to FIG. 1, a related art substrate bonding apparatus includes a frame 10, an upper stage 21, a lower stage 22, a sealant dispenser (not shown), a liquid crystal dispenser 30, an upper chamber unit 31, a lower chamber unit 32, chamber moving means, and stage moving means. The sealant dispenser and liquid crystal dispenser 30 are mounted at side positions of the frame 10. The upper chamber unit 31 can be selectively joined to the lower chamber unit 32. The chamber moving means includes a driving motor 40 for moving the lower chamber unit 32 to position S1, where sealant material and liquid crystal material can be dispensed onto a substrate, and to position S2, where substrates can be bonded together. The stage moving means includes a driving motor 50 for raising and lowering the upper stage 21 before, during, and after the substrates have been bonded. Having described the related art substrate bonding apparatus above, the process by which the related art substrate bonding apparatus fabricates an LCD device will now be described in greater detail below.
To fabricate an LCD device using the related art substrate bonding apparatus described above, a first substrate 51 is held by the upper stage 21 while a second substrate 52 is held by the lower stage 22, as shown in FIG. 1. Next, the chamber moving means moves the lower chamber unit 32, supporting the lower stage 22, to the position S1. Subsequently, sealant material and liquid crystal material are dispensed onto the second substrate 52 held by the lower stage 22. After sealant material and liquid crystal material are dispensed onto the second substrate 52, the chamber moving means moves the lower chamber unit 32 to position S2, as shown in FIG. 2, whereby the first and second substrates 51 and 52, respectively, can be bonded together. With the lower chamber unit 32 at position S2, the chamber moving means joins the upper chamber unit 31 to the lower chamber unit 32. Upon being joined, the upper chamber unit 31 and the lower chamber unit 32 define an interior space that encloses the upper and lower stages 21 and 22, respectively. Using a vacuum means (not shown), the interior space is evacuated to create a vacuum. Within the evacuated interior space, the stage moving means lowers the upper stage 21 such that the first substrate 51, held by the upper stage 21, moves toward the second substrate 52, held by the lower stage 22. As the upper stage 21 descends, the first and second substrates 51 and 52, respectively, become bonded to each other, thereby completing fabrication of the LCD device.
Fabricating LCD devices using the related art substrate bonding apparatus, however, is disadvantageous because the upper stage 21 holds the first substrate 51 by transmitting a suction force to operably proximate portions of the first substrate 51. Due to the dimensions and weight of the first substrate 51, some portions of the first substrate 51 may not be operably proximate the upper stage 21. For example, peripheral portions of the first substrate 51 may be sufficiently close to the upper stage 21 (i.e., operably proximate) to be affected by the transmitted suction force. However, due to the weight of the first substrate 51, interior portions of the first substrate 51 may be spaced apart from the upper stage 51 (e.g., sag) by a distance which is outside the range (i.e., not operably proximate) in which the transmitted suction force may affect the first substrate 51. Accordingly, the upper stage 21 may not effectively transmit a suction force to those portions of the first substrate 51 that are not operably proximate to the upper stage 21.
Related art attempts to prevent the aforementioned sagging phenomenon from occurring have been met by increasing the suction force transmitted by upper stage 21 to the first substrate 51. However, the first substrate 51 may become damaged if the transmitted suction force becomes excessive. As display areas of LCD devices continues to increase, methods and apparatuses capable of safely and effectively transmitting suction forces from upper stages to corresponding substrates must be developed.